Aetna Inc., a leading healthcare service provider, outsources responsibility for the daily operation of more than 5 million square feet of company-owned commercial property in the Northeastern U.S. to Grubb & Ellis Management Services (GEMS). As one of the few real estate management companies with a comprehensive menu of full-time in-house engineering services, GEMS provides its customers with a wide range of coverage, including demand-side energy management, identification and analysis of energy reduction opportunities, usage monitoring and analysis, and other services.

Two-thirds of the office space in Aetna’s modern, multi-use facility in Windsor, Conn., is leased by a pair of high-profile IT companies, including a well-known financial services group and a large commercial printer specializing in custom mailing applications for high-volume accounts. Though similar in many ways, the unique energy patterns of these high-use tenants prompted the owner to find a way to monitor individual energy consumption to more accurately and fairly bill facility lessees.

Concise Energy Snapshots

As project engineer for several GEMS company properties, Mark Melnick designs and implements a full spectrum of engineering projects, including monitoring and maintaining energy usage data for utility budget development and energy contract negotiations. Melnick’s solution for the Windsor facility was to install a full-featured automatic meter reading (AMR) system that would provide an accurate, concise snapshot of each tenant’s energy usage, in lieu of the usual cost-per-square-foot allocation used by many commercial property managers.An important requirement, scalability was seen as a definite plus should the existing tenants require additional monitoring or the remaining unoccupied third of the facility be leased to a new tenant.

After investigating alternative solutions, Melnick selected Langhorne, Pa.-based E-Mon, LLC (www.emon.com), based on the availability of East Coast-based technical support and positive feedback from other users. In a test of system accuracy, Melnick “compared the readings gathered from the E-Mon submeters to test equipment that was installed temporarily, and the readings between the two systems were very similar.”

The submetering system was installed in two phases, with the commercial printer waiting on completion of the financial services company. “Each phase of the system took approximately three to four weeks to install,” said Melnick, “which may seem a bit long, but all the conductors were run in-pipe and a large portion of the install was above very crowded suspended ceilings.” The installation was performed by Windsor Locks-based P.J. Lodola & Sons Electrical Contractors.

Submetering the Operational Parameters

In operation, the submetering system monitors three separate parameters - 480V/3-phase electrical power, both AC line and battery-backed Uninterruptible Power Supply (UPS) systems, and chilled water consumed by the facility’s HVAC system. Figure 1 shows the process by which the electrical power and chilled water input data are converted into information for analysis and tenant billing.

Split-core current sensors allow meter hook-up to the 480V line without powering down the load being measured, resulting in a safer, quicker install.The wiring distances between the panels and the E-Mon Class 3000 submeters vary from a few feet to several hundred feet. The meters themselves are daisy-chained via an RS-485 link that allows up to 4,000 feet total length from the farthest sensor to the central monitoring location.

The second measurement, consisting of two data points, is taken from battery-backed UPS systems.Since it’s billed at a higher rate than normal power to help defray the owner’s UPS maintenance costs, back-up power is tracked as a separate line item. Each UPS battery array is therefore connected to its own submeter, which sends a digital output to the lead or master meter in the chain.